1. Field of the Invention
The invention relates to disintegrant granulate compositions of cellulose and optionally cellulose/starch derivatives, polymeric binders and gel-forming surfactants, as well as methods for making these compositions. These disintegrant granulate compositions are suitable, for example, as disintegrants for detergent tablets and granulates.
Disintegrants for tablets or granulates are auxiliary agents which promote the disintegration of tablets or granulates upon contact with liquids, particularly water. The purpose of the disintegrant is to cause and enhance both the disintegration of tablets into coarse fragments, as well as the subsequent disintegration of the coarse fragments into smaller particles. In the case of detergent tablets or granulates, the use of a disintegrant ultimately results in the dissolution and/or dispersion of all of the detergent components.
Tablets are produced by compressing a starting granulate using, such that the bulk density of the granulate, which is about 900 g/l in compact detergents, for example, rises to 1200 g/l after tabletting. As a rule, such tablets, which have higher densities than the starting granulate, have poorer solubility and reproducibility compared to the starting granulate. The addition of disintegrants promotes the desired rapid dissolution, or disintegration and dissolution of such tablets.
Depending on the composition of detergents and cleaners, the molding pressures required in tabletting can vary. Thus, the type of builder used, e.g. phosphate, zeolite, disilicate or layered silicate, may require various different molding pressures, so that tablets having varying hardness or compactness are formed. In order to safely protect the tablets against external mechanical impact, e.g. against breaking during transportation or when dropped, they should have a strength of 50 N or more.
Two ways of introducing a detergent tablet into a washing machine are normally possible: placing the tablet into the wash-in chamber of the washing machine, or into the washing drum of the washing machine. The requirements for tablet disintegration will vary depending on where the tablet is introduced into the washing machine.
Introduction into the wash-in chamber is the easiest method for the user and provides a higher quality washing process. However, this method places exceedingly high demands on the disintegration rate of the tablet. Specifically, the first step of tablet disintegration into coarse fragments must proceed very quickly because otherwise, tablet residues remain in the wash-in chamber and will not be utilized in washing. In modem washing machines, a time period of about 30 seconds normally is available for content of the tablets to be washed into the washing drum of the washing machine, via the wash-in chamber. In addition, this disintegration must occur within this 30 second period in both hot or cold wash-in water. When the detergent tablet is placed directly into the washing drum, the conditions for tablet disintegration are quite different because both mechanical friction and increasing water temperatures assist in the tablet dissolving process
This problem of highly compacted moldings having long disintegration times is well-known in the field of pharmaceutical preparations. A large number of compounds and mixtures are known as tablet disintegrants in pharmaceutical practice. Several modes of operation have been discussed for tablet disintegrants, such as evolution of gas bubbles (effervescent powders), mutual repulsion of particles, transport of water (wicking effect), and a swelling/expansion due to absorption of water.
Many compounds which undergo massive swelling upon exposure to water are known. However, the swelling rate of these compounds is frequently is too slow to be of practical use. In addition to swelling rate and swelling volume of such compounds, the swelling pressure is of particular importance. There are various known methods for measuring these properties. It is possible to measure the expansion with no counter-pressure, and also to measure the swelling pressure with no expansion. Combined methods of measuring, wherein both the swelling pressure and the expansion are detected, are particularly suited in making predictions as to the suitability of disintegrants in tablets. One such method is the measurement of the swelling kinetics of the disintegrant, where the time dependence of the expansion under load of a disintegrant is determined. Hence, both swelling pressure and expansion are included in the results. Products suitable as disintegrants are also known to undergo either linear or non-linear expansion during the swelling process. Owing to their more rapid effect, disintegrants which undergo nonlinear swelling are markedly superior to disintegrants which undergo linear swelling.
2. Discussion of the Background
As can be inferred from the statements in WO 98/55575 regarding the prior art, the disintegrants known in the production of drug tablets may also be used in the field of detergents and cleaners.
DE-OS 2,251,249 describes rapidly disintegrating drug tablets, for example, which are produced by compressing a drug granulate and a disintegrant granulate. The use of granular starting materials results in a porous tablet structure. A starch-based disintegrant granulate having a particle size of from 2.0 to 0.3 mm is used as an example.
DE-OS 2,355,204 reports drug tablets which for tablet stability reasons are compressed from granular starting components adjusted to a moisture content of less than 2%, prior to compression.
U.S. Pat. No. 3,629,393 claims drug tablets with delayed release of the active ingredient, which are compressed from granular components, including granular disintegrants comprised of high molecular weight water-swellable compounds such as cellulose derivatives. The examples describe granulate dimensions of around 0.84 mm.
U.S. Pat. No. 4,072,535 describes the use of disintegrants made of pre-compacted starch in pharmaceuticals and detergents. The grain size of the compacted material is from 0.05 mm to 0.42 mm, the moisture content is reported to be 9-16%, preferably 11-13%. The disintegration times of the exemplary tablets are around several minutes.
DE-OS 2,321,693 reports detergent tablets containing from 1 to 25 wt.-% of fibrous cellulose as disintegrant. In the examples, tablets containing compacted cellulose granulates have astrength of from 15 to 19 N.
EP 0,170,791 describes tablet-shaped detergent additives compressed from granulate components, having from 1 to 5 wt.-% of granulate tablet disintegrants based on crosslinked polyvinylpyrrolidone and/or cellulose ethers. The granulate should be free of dusty components. The tablets have breaking strengths of from 50 to 120 N and long dissolution times of several minutes.
WO 98/40463 reports moldings having detergent or cleaning activity, which are produced using a disintegrant granulate having a high adsorptive capacity for water and a grain size distribution in which at least 90 wt.-% of the grains have a particle size of 0.2 mm to 3 mm. The fraction of dust particles having a particle size &lt;0. 1 mm is below 1 %. The disintegrant granulate contains at least 20 wt.-% of disintegrants such as starch, starch derivatives, cellulose, and cellulose derivatives. According to the teaching of this patent, the presence of anionic or non-ionic surfactants has a negative effect on the tablet disintegration time. The granulate is produced in a conventional fashion, such as by spray drying, superheated steam drying of aqueous formulations, or by granulating, pelletizing, extrusion, or roll compacting of powdered components. There is no detailed processing data as to the granulation process or other processing steps following granulation to form the disintegrant granulate. The detergent tablet produced as an example includes a disintegrant based on compacted cellulose made of thermomechanically treated wood material and has a tablet hardness of 45 N. Tablets having higher strength, i.e. more than 50 N, were not described.
WO 98/55575 describes an auxiliary agent granulate for moldings having detergent and cleaning activity. The claimed auxiliary agent granulates include from 10 to 95 wt.-% of cellulose having a particle size below 0.1 mm and from 5 to 90 wt.-% of microcrystalline cellulose. According to the Examples, the celluloses in the auxiliary agent granulates are partially combined with carboxymethylcellulose, N,N,N',N'-tetraacetylethylenediamine (TAED) and citric acid/bicarbonate. The grain size of more than 90 wt.-% of the compacted material is from 0.3 to 2.0 mm, and 0.2 mm in less than 5 wt.-% of the compacted material. There are no dusty components. Roller compaction of the dry pre-mixture is the preferred method of production. WO 98/55575 does not provide detailed processing data for the production of the granulate. The examples show that detergent tablets which have the auxiliary agent granulates, have low strengths of 35 N or less. More stable, more highly compacted tablets having higher strengths of at least 50 N are not described.
The unpublished European Patent Applications 98 121 397.8 and 98 121 392.9 claim cellulose/cellulose derivatives and starch/starch derivatives, respectively, together with thickening surfactants and fine particulate polymers of (meth)acrylic acid in a compacted, granulate form as a disintegrant granulate component of detergents and cleaners, softeners, and stain removing salts produced in the form of tablets. The granulates have non-linear swelling kinetics such that--with respect to the overall swelling process--a massive increase in volume occurs during the initial phase of the swelling process. This reference does not describe the dissolution behavior of the tablets in the wash-in chamber of a washing machine.
The patent application WO 98/40462 describes a pellet made of powdered and/or granulate ingredients, particularly detergent ingredients, and includes particles of a cellulose-containing material, which may also be present in compacted form, acting as a disintegrant.
Particularly preferred cellulose components include pulps treated by thermomechanical (TMP) and chemithermomechanical (CTAP) processes. The particle size of the compacted disintegrant may range from 0.2 to 6 mm. Surfactants may also be added to the pellet via the cellulose component, for example at a level of 0.5 to 5% of surfactant/pellet. This corresponds to a surfactant content of about 1445 wt.-% in the cellulose disintegrant, based on the reported 3 to 6%/pellet concentrations of cellulose disintegrant in the compacted granulate. This reference does not provide detailed process or technical information regarding the production of the disintegrant granulate or its function in the pellet.
According to EP 0,750,662 B1, the production of cleaning tablets having high breaking strength and storage stability is possible when the components of the mixture are first made hydrophobic, and the tablets are then produced without water. These tablets do not include any disintegrant granulates and have breaking strengths of &gt;150 N, but they exhibit highly delayed dissolution behavior.
The prior art also includes the products marketed by the company Degussa AG, designated Elcema G250 and Elcema G400, which consist of pure compacted cellulose, and have been used as tablet disintegrants since 1971. These products are produced using dry granulation and have a particle size of from 0.03 up to 0.40 mm. The moisture content is less than about 6%.